how long immunity vaccinated mothers pass on to their babies and the key to breastfeeding

Some scientific studies already report that pregnant women who have been vaccinated against SARS-CoV-2 can give you natural immunity passive (transferred from mother to fetus) to their babies. The presence of neutralizing antibodies in umbilical cord blood and breast milk suggests this possibility.

News of the first baby born with COVID-19 protection broke in March when a vaccinated woman gave birth to a daughter in Florida. Later they appeared new cases in different regions of the map like Israel, Spain, Mexico and Brazil.

As they were excluded from the initial phase 3 clinical trials, data is limited regarding the efficacy and safety of COVID-19 vaccination during pregnancy and postpartum. From the end of 2020 to today, consensus guidelines have been published with a predominant precautionary approach.

According to the World Health Organization (WHO), infected pregnant women have more risk to require hospitalization in intensive care and mechanical ventilation, compared to another of the same age who was not pregnant. Faced with these data, the province of Buenos Aires includes as new population group at risk pregnant, postpartum or breastfeeding women.

Babies with antibodies

Néstor Vain, head of neonatology in the sanatoriums of Trinidad Palermo San Isidro and Ramos Mejía and Patricia Glasman, infectious pediatric doctor, explain that during pregnancy there is normal transfer of antibodies (immunoglobulins) from mother to fetus through the placenta to provide essential protection during the first months of life.

“The passage begins during the first termand increases exponentially as the pregnancy progresses (the placenta thins). In general, antibodies transferred via the placenta last for 2-6 months in baby, although premature babies will have lower levels compared to term newborns, ”they detail.

They also point out that the antibody transfer process is influenced by factors such as gestational age, maternal immunity, concomitant infections, levels of specific antibodies acquired after vaccination, and placental integrity.

For his part, Jorge Quarleri, biochemist and principal investigator at Conicet, sees maternal vaccination as an excellent opportunity to reduce the risk of disease in the mother, fetus and baby and argues that intrauterine immunity is fundamentally constituted by commonly known immunoglobulins (Ig). as antibodies (according to their properties, there are 5 known classes: IgG, IgA, IgM, IgD, IgE).

“IgGs are the most abundant in our blood and have greater neutralization capacityIn other words, it is the one that most effectively prevents a virus or toxin from coming into contact with a cell. In addition, it is the only immunoglobulin capable of passing from maternal blood to the fetus by crossing the placenta, ”he emphasizes.

And he continues that IgG binds to specific receptors that allow it to be transported from maternal blood to fetal blood. To understand the dynamics, he suggests imagining a “swivel chair” located on the mother’s side where only IgG can sit and after that it spins and releases it into the blood of the fetus.

Both that generated after a natural infection that the mother could have suffered and that induced in response to a vaccine have the possibility of passing to the fetus (the “rotating chair” works without discriminating the origin of these IgGs).

Most IgG transfers occur after 28 weeks of gestation. “As the pregnancy progresses and the placenta grows in cell mass, the expression of IgG receptors could increase and with this the rate of antibody transport will be higher,” he emphasizes.

The United States Centers for Disease Control and Prevention has recommended that pregnant and breastfeeding women have access to available dosages.

“There are still no specific recommendations regarding when to apply during pregnancy. Those who could benefit most from an early vaccination strategy are pregnant women at high risk to SARS-CoV-2 as health workers, or those with some comorbidity such as gestational diabetes and high blood pressure, according to Leda Guzzi, an infectious disease doctor, member of SADI.

“Theoretical risks of vaccination with COVID-19 during pregnancy and breastfeeding are limited. We have at least one report that has studied the safety of mRNA-based vaccines in nearly 36,000 pregnant women (and includes a portion of women who received the vaccine during the peri-conceptual period) where they are presented as safe. », Says Quarleri and emphasizes the need to continue the follow-up studies for longer periods.

According to a study by Weill Cornell Medicine and New York published in Obstetrics & Gynecology, women who receive COVID-19 mRNA vaccines produced by Pfizer-BioNTech or Moderna during their third trimester of pregnancy may develop a strong immune response and passage of antibodies umbilical cord blood protectors to their babies.

Marta Cohen, pediatric pathologist, points out that among the doses available in Argentina, Oxford-AstraZeneca or Sputnik V could be considered (not Sinopharm because it inactivated the virus).

“Vaccines have to have components or be genetically engineered like those from Pfizer. Have no inactivated or living viruses. Although those who received two doses have a higher level of antibodies in the umbilical cord blood, with a dose of antibodies are also generated (to a lesser extent) ”, he explains and underlines the importance for pregnant women to take care of themselves and to be vaccinated because they constitute a population at risk.

Vaccination and breastfeeding

Roxana Conti, pediatrician and neonatologist, member of the SAP National Breastfeeding Committee, promotes the importance of breastfeeding, which she calls the “first vaccine” because breast milk is transferred protective antibodies (they can reach breast milk through the enteromammary mechanism) against diseases to which mothers have been exposed throughout their lives and also confer antibodies generated by vaccines the mother has received. In addition, he points out that breast milk has immunomodulators that promote the development of the baby’s immune system.

For this reason, it is categorical that the days after birth constitute a sensitive period, during which the close contact between mother and newborn infants long-term positive effects on the interaction. “All the more so in the context of a pandemic, it is important to start and maintain breastfeeding as indicated by the WHO (exclusive until the sixth month then, continued until two years or more)”, he says and refers that on May 21 the World Day for the Protection of Breastfeeding has been celebrated.

In a study published in the journal JAMA (performed in Israel), which included 84 lactating women (504 samples) vaccinated with Pfizer, it was detected 61.8% IgA antibody (two weeks after inoculation) in breast milk and increased to 86% one week after the second dose. IgG antibodies were 91.7% effective at week 4 (1 week after the 2nd dose) and increased to 97% at weeks 5 and 6 after vaccination. Both, quantified with a high neutralizing power.

Although the duration of protection and anti-SARS-CoV-2 antibodies in breast milk is unknown, Guzzi suggests that if we extrapolate what is happening with other infectious diseases, in which the mother can breastfeed the baby, the passage of antibodies with milk is produced during the lactation period.

Antibodies that the mother gives to the fetus in her womb (passing the placenta) or to the newborn (through milk and colostrum) to immunoglobulins have a half-life, according to Quarleri. What does mean? They will be metabolized (broken down) over time and therefore their duration is limited and they can remain in the child for months after birth. And he adds: “During this time, the newborn must have been able to have had its own immune response that began as early as intrauterine life.”

PS